協議傳值

協議傳值是利用協議的特性來實現界面傳值的一種方法.
我們把要傳值得頁面當作協議聲明者,把接收值得頁面作為代理人
讓代理人執行協議方法,從而將值傳到接收頁面

下面我們來看一下協議傳值的具體步驟:

首先要明白簽訂協議的完整步驟:
1.聲明協議
2.聲明代理人屬性
3.讓代理人執行協議方法
4.簽訂協議
5.指定代理人
6.實現協議方法

下面來看一下代碼實現:

AppDelegate.m的實現過程在這里不在重復給出,具體步驟可以到我的上一篇文章里閱讀:(Objective-C界面傳值(一):屬性傳值)

ViewController.m

#import "ViewController.h"
#import "SecondVIewController.h"
#pragma mark 4.簽協議
@interface ViewController ()<PassValueProtocol>

@property(nonatomic, retain) UITextField *textField;

@end

@implementation ViewController

- (void)dealloc
{
    [_textField release];
    [super dealloc];
}

- (void)loadView
{
    [super loadView];

    self.textField             = [[UITextField alloc] initWithFrame:CGRectMake(100, 100, 175, 50)];
    self.textField.placeholder = @"請輸入文本";
    self.textField.borderStyle = UITextBorderStyleRoundedRect;
    [self.view addSubview:_textField];
    [_textField release];

    UIBarButtonItem *rightButton           = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(didClickedRightBarButton:)];
    self.navigationItem.rightBarButtonItem = rightButton;
    [rightButton release];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor whiteColor];
    self.navigationItem.title = @"首頁";
    self.navigationController.navigationBar.barStyle    = UIBarStyleBlack;
    self.navigationController.navigationBar.translucent = NO;
}

#pragma mark 按鈕點擊方法
- (void)didClickedRightBarButton:(UIBarButtonItem *)button
{
    SecondVIewController *vc2 = [[SecondVIewController alloc] init];
#pragma mark 5.設置代理人
    vc2.delegate              = self;
    //從第一頁向第二頁傳值依然采用屬性傳值
    vc2.secondString          = self.textField.text;
    [self.navigationController pushViewController:vc2 animated:YES];
    [vc2 release];
}

#pragma mark 6.實現協議方法
- (void)passString:(NSString *)string
{
    self.textField.text = string;
}

SecondViewController.h

#import <UIKit/UIKit.h>

#pragma mark 1.聲明協議
@protocol PassValueProtocol <NSObject>

- (void)passString:(NSString *)string;

@end

@interface SecondVIewController : UIViewController
/**
 *  屬性傳值字符串
 */
@property(nonatomic, copy) NSString *secondString;
#pragma mark 2.聲明代理人屬性
@property(nonatomic, assign) id<PassValueProtocol> delegate;

@end

SecondViewController.m

#import "SecondVIewController.h"

@interface SecondVIewController ()

@property(nonatomic, retain) UITextField *textField;

@end

@implementation SecondVIewController

- (void)dealloc
{
    [super dealloc];
}

- (void)loadView
{
    [super loadView];

    self.textField             = [[UITextField alloc] initWithFrame:CGRectMake(100, 100, 175, 50)];
    self.textField.placeholder = @"請輸入文本";
    self.textField.text        = self.secondString;
    self.textField.borderStyle = UITextBorderStyleRoundedRect;
    [self.view addSubview:_textField];
    [_textField release];

    UIBarButtonItem *leftButton           = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(didClickedLeftBarButton:)];
    self.navigationItem.leftBarButtonItem = leftButton;
    [leftButton release];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor whiteColor];
    self.navigationItem.title = @"第二頁";
}

#pragma mark 按鈕點擊方法
- (void)didClickedLeftBarButton:(UIBarButtonItem *)button
{
#pragma mark 3.代理人執行協議方法
    [self.delegate passString:self.textField.text];
    [self.navigationController popViewControllerAnimated:YES];
}

需要注意的幾點:

• 1.協議的6步一定不能缺少
• 2.代碼塊中只是寫了需要用到的幾個方法的內容,系統自動生成的方法請不要隨便刪除
• 3.控件設計坐標是根據iPhone6或iPhone6s尺寸寫的,并沒有做適配.

效果圖:

首頁框中輸入字符串,點擊"Add"

屬性傳值成功

在第二頁文本框中輸入字符串,點擊"Cancel"

協議傳值成功